Non-simultaneous ignition is a concern, but the Blue Thunder propellant in G80's lights easier than some other propellants, so I think it's less of one. It might be a good idea to test some spare igniters on whatever equipment will be providing power to them and make sure it will start four igniters simultaneously.
When I look at this rocket, my biggest concern is with it shredding. It's kind of like four minimum diameter rockets stuck together with four punchy (high-thrust-fast-burn) motors. I would worry about the joints between your main and outboard tubes. That said, I see what looks like a pretty thick fillet between the tubes, so perhaps you had the same thought. As far as stability goes, my rough mindsim says long and skinny makes it okay, but my more cautious side worries about those three noses on your outboards. They look like the solid urethane noses from PML and if they are, it might be a large amount of weight to have that far back, but I could be wrong. Have you tried building this in OpenRocket/Rocksim?